Acrylic coating compositions are widely used for finishing automobiles and trucks. With the development of 2-layer finishing systems in which a clear, unpigmented topcoat is applied over a colored basecoat, acrylic compositions have been used for both topcoat and basecoat.
With the incorporation of both polymeric and elastomeric parts as exterior body components, a need has arisen for finishes which can be applied to these surfaces as well as to metal. In addition to basic adhesion requirements, the curing characteristics and durability are important considerations in a coating that can be successfully applied to both metal and non-metal automotive finishes. It is widely recognized that a hard finish, when applied to a non-metal surface, will not only tend to crack itself, but will actually depreciate the strength of the substrate onto which it is coated. In addition, a coating which is to be simultaneously applied to metal and non-metal surfaces must be able to withstand the curing conditions that are applicable to both. For example, when an automobile is exposed to an elevated temperature for a given period of time, a metal substrate will conduct heat to the coating on that substrate more quickly than a non-metallic substrate. Thus, the same coating applied to metal and non-metal parts is exposed to elevated curing temperatures for different periods of time, depending on the substrate to which it is applied.